Electrooptical system



March 5,1935. H. g. lvEs ELECTROOPTICAL SYSTEM Filed. Feb. 5, 1930 A rTURN; Y

Patented Mar. 5, 1935 UNITED STATES PATENT OFFICE TelephoneLaboratories, Incorporated,

New

York, N. Y., a corporation of New York Application February 3,

6 Claims;

This invention relates to electro-optical systems and more particularlyto the production of an image having -a predetermined color.

' '-It has heretofore been proposed to reproduce '5 an image of movingobjects or pictures in their natural colors. In such systems, the lightderived from the object scanned at the transmitting station is appliedto photoelectridcells each of which is sensitive to light rays lyingwithin 10 :certai-n portions of the light spectrum, i. e. certaincolors, 'toproduc'e separate and distinct currents. Each current variesin accordance the'lig h't'intensities o'f elemental "areas of the objectpossessing the-corresponding color. The 15 currents corresponding to thediltrent portions of the spectrum are separately transmitted to areceiving station, where "they are respectively used to energize sourceseach adapted to pro- "duce light corresponding to the selected portion 2of the spectrum.

other words, the current corresponding to one color of the objectscanned at the trarmm-itting station is separately transmitted tocontrol the production "of light of the same color at the 25 receivingstation, where the colors are blendedor mixed to produce color effectscorresponding to the natural colors of the object scanned.

In certain systems currents corresponding to the different primarycolors are transmitted over "1 ,0 'difierent channels, as disclosed, forexample, in

U. S. Patent 13878147, issued September 20, 1932 to H. E. Ives. In othersystems the separate currents are transmitted successively over the samechannel,

" 5 as disclosed in U. S. Patent 1,839,361, issued January '5, 1932 toWeaver and Branson.

'In still other systems, voltage discrimination is used to separate thecurrents arriving at a receiving station, and the respective currentsare 40 used to control light sources, each producing :a distinct primarycolor. y

The present invention provides a system in which a single current )band,varying in accordance with the tone values of elemental areas #45 of anobject "or ffi-eldis'canne'd at a transmitting 1930, Serial No. 425,432

object scanned but which is variable in accordance with the tone valuesof its elemental areas, to produce light radiations giving the effect ofa predetermined color which differs from that supplied by the separatesources. I

In one embodiment, which will be hereinafter described in detail by wayof example, a current band is supplied to a plurality of light sourcesconnected in parallel. The band is independent of the natural colors ofthe scanned '10 object, but its .amplitude varies in accordance with thelight intensities of elemental areas of the object.

Each source is adapted to produce light of a color different'from theother and varying in intensity with the changingamplitudes of theapplied current band. The light radiations supplied "by the respectivesources are superposed on each other, or are supplied to color mixingmeans, to produce illumination which gives the effect of pure whitelight. Obviously, by properly controlling the color of the lightradiations supplied by the respective sources and superposed upon eachother, the combined light may give an'effe'ct corresponding to anydesired :color. 5

Fig. 1 is a schematic of a television system involving the invention,and

Fig. *2 illustrates apparatus which may be substituted for that to theright of section line -AA in Fig. 1.

The transmitting station T shown in Fig. :1 includes apparatus similarto and operable in the manner disclosed in application Serial No. 227,-649 filed Oct. 2-1, 1927 by F. Gray. Briefly it comprises a source oflight 1 from which light 5 rays are directed by an optical system 2 inthe form of a beam upon a peripheral portion of a rotating disc 3provided with apertures arranged in a spiral, whereby "as the diskrotates, a pencil of light traverses each aperture, as it passes '40across the beam produced by the system "2, and is directed upon theobject or field. 5 to be scanned for transmission, by the movement ofthe aperture and the action of lens 4.

The apertures in the disc are of such size and. are so arranged that, asthe disc rotates, the traveling pencils produce spots of light whichtraverse successive strips or lines of the object or field 5, which isthus completely illuminated once per complete revolution of the disc.

'lliight is reflected from the object 5 upon the light sensitive system;6, that may include one or more photoelectric cells, which is therebyactivated 'to cause the production of an electric current band theamplitude of which varies in accordance with the tone values ofelemental areas of the object.

The current band of variable amplitude, after amplification in thedevice '7, is transmitted by means of a communicating medium, hereinshown as a transmission line 8 but which may be a radio channel, to aremote station R where it is again amplified, by the device 9. Thedevices 7 and 9 are shown as including space discharge tubes, but anyother form of distortionless amplifier may be used.

It is to be understood that in operation heating current will besupplied to the filaments and space current to the filament-anode pathor" the tubes included in devices '7 and 9, and, if desirable, biasingpotentials to their grids.

The amplified current wave is supplied to three parallel connected.lamps 10, 11 and 12, each of which produces light of a color difierentfrom that radiated by the others. Any type of lamp may be used, providedthe intensity of the light produced by it varies synchronously withvariations in value of the current supplied by the amplifier.

Associated with the respective lamps 10, 11 and 12 are color filters 13,14 and 15 and two semi-transparent mirrors 16 and 1'7.

The light radiations supplied by sources 10 and 12 after passing throughthe filters 13 and 15 are superimposed upon those emanating from source11. r

The filters serve to determine the exact color of the radiationssupplied by the respective sources to the mixing or blending means andhence the color effect given by the light which results from combiningthe radiations. By properly selecting the filters, the color effectgiven by the combined light may be any one of a number of tints.

For example, lamp 10 may supply red light, lamp 12 blue light and lamp11 green light. When these different colored radiations are properlycontrolled as to their respective intensities and are superimposed uponeach other, or are combined, the resultant illumination gives to thehuman eye the impression of white light.

Obviously by changing the intensities of the light supplied by one ormore of the lamps 10,

'11 and 12, or by using lamps producing radiations of other than theabove mentioned primary colors, the combined radiations will produce inthe human eye the effect of light having a definite color.

The combined radiations may be caused to produce the effect of any fixedtint or color by maintaining substantially invariable the relativeintensities of the colors which are blended during non-signalingperiods. When the image current wave is supplied to the lamps, theintensity of the light produced by the combined radiations will bevaried, but its color will remain the same.

The receiving apparatus includes a scanning disc 18 provided with aspiral row of apertures and operated in synchronism with the disc 3 ofthe transmitter.

The system of lamps 10, 11 and 12 and disc 18 cooperate to produce,within the field of vision of the observer 19, an image of the objectscanned at the transmitter.

In order that no light may be supplied to the observer except throughthe apertures in the disc 18, the lamp system 10, 11 and 12 should beenclosed or shielded. A shielding element is shown at 20.

Fig. 2 illustrates a simplified apparatus for producing a televisionimage having a selected or predetermined color. This apparatus comprisestwo lamps 21 and 22 respectively producing light rays of differentcolors, a single color filter 23, and a single semi-transparent mirror24 for superposing the radiations from 21 upon those supplied by 22.

As a practical example the lamps 21 and 22 may be glow discharge lamps,one of which is charged with neon and the other with argon. Associatedwith the argon filled lamp is a filter which emphasizes the blue-greenof the spectrum of its radiations and thereby renders them complementaryto the orange-red of the neon lamp. Thus the basic color of the imageseen by the observer will be white.

Obviously the basic color of the image may be modified, by using afilter which emphasizes certain selected spectral lines of theradiations produced by the argon or neonlamp.

What is claimed is:

1. In an electro-optical system, a receiver comprising a plurality ofsources each producing light radiations of a difierent color, means forapplying to said sources a current variable with the tone values ofelemental areas but independent of the color of an object scanned, meansfor blending the radiations from said sources to produce illuminationgiving the effect of a single color diifering from those of theradiations, and-means for utilizing the blended illumination to producean image having the same color characteristic throughout.

2. An electro-optical receiver comprising a plurality of lampsrespectively supplying light radiations of different colors, means forcontrolling said lamps by a current variable with the tone values ofelemental areas but independent of the color of an object scanned, acolor filter associated with at least one of said lamps, means forcombining unfiltered and filtered radiation to produce light giving theeffect of a single color different from that of the constituentradiations, and means for utilizing the combined radiations to producean image having the same color characteristic throughout.

3. The method of operating the receiver of an electro-optical systemwhich comprises continuously producing from a single current, havingvariations representative of the tone values of an object an image ofwhich is to be produced, a plurality of currents each of which varies inthe same manner as said single current, simultaneously and separatelycontrolling the production of light radiations of different colors bysaid latter currents respectively, blending the resultant radiations toproduce composite light capable of producing the effect of a singlecolor, and utilizing this composite light of unchanging colorcharacteristic to produce an image having this color characteristicthroughout.

4. In an electro-optical system, an image producing apparatus comprisinga plurality of light sources each producing light radiations of adifferent color, said radiations when combined giving the effect ofsubstantially white light, means for applying to said sources a currentthe amplitude of which is representative of the tone values of elementalareas of the object an image of which is to be produced but independentof the color of said object, means for blending the radiations from saidsources to produce substantially white illumination, and means forutilizing the blended radiations to produce an image in substantiallywhite and black and intermediate tone values.

5. In an electro-optical system, image producing apparatus comprising aneon filled glow lamp, an argon filled glow lamp, a color filterassociated with one of said lamps of such characteristic that theradiations therethrough from said lamp when combined with radiationsfrom the other of said lamps gives the effect of substantially whitelight, means for simultaneously applying to said lamps a current theamplitude of which is representative of the tone values of elementalareas of the object an image of which is to be produced but independentof the color of said object, means for blending the radiations from saidlamps to produce substantially white illumination, and means forutilizing the blended radiations to produce an image in substantiallywhite andblack and intermediate shades;

6. In an electro-optical system, an image producing device comprisingthree light sources respectively radiating light of different color,

means for applying to said sources a current whose amplitude isrepresentative of tone values of elemental areas of the object the imageof which is to be produced but independent of the color of said object,means for blending the resulting radiations, and means for utilizing theblended radiations to produce an image appear-' ing throughout to havesaid color difierent from that of the radiations from any of saidsources.

HERBERT E. IVES.

